Alteration of testicular biochemistry during protein restriction in nickel treated rats

Nickel sulfate (2.0 mg/100 g.b.wt) dissolved in double-distilled water was administered (ip) on alternate days for ten doses to normal protein-fed and protein-restricted Wister strain albino rats (b.wt. 160 ± 5 g). Two groups were used: one with normal protein diet, whereas the other with protein-restricted diet served as control. Twenty-four hours after the last treatment, the animals were sacrificed by decapitation. Tissues such as the testes, seminal vesicles, epididymis (Cauda and Caput) and prostate were dissected out, wiped clean, and stored at -20‡C until analysis. Lactate dehydrogenase (LDH) activities, glutamate oxaloacetate transaminase (GOT) activities, glycogen content, cholesterol content, and total protein content of the testes were estimated. Nickel sulfate administration significantly decreased the body weight of both normal protein-fed and proteinrestricted groups of animals; the organ weights were also decreased. Significant decrease of LDH activity was observed, but GOT activity was not altered significantly. Testicular glycogen and cholesterol increased significantly in both experimental groups, but total protein content decreased. Nickel sulfate seems to have an adverse effect on the male reproductive system in both groups of animals fed with normal protein (18% casein) diet and protein restricted (5% casein) diet.     

Characterization of a novel low molecular weight sucrase from filamentous fungus Termitomyces clypeatus

An extracellular sucrase from the culture filtrate of filamentous basidiomycota Termitomyces clypeatus grown on high sucrose (5%, w/v) was purified by gel filtration chromatography, ion exchange chromatography and HPGPLC. The biochemical properties, molecular weight and conformation of sucrase produced were significantly different from the sucrase earlier purified from sucrose (1%, w/v) medium in the fungus. Purified sucrase was characterized as a low molecular weight protein of 13.5 kDa as approximated by SDS-PAGE and HPGPLC and exhibited predominantly random coil conformation in far-UV CD spectra. The enzyme was optimally active at 47 °C and pH 5.0. K_m and catalytic activity of the enzyme for sucrose were found to be 3.5 mM and 1.06 U/mg/mM, respectively. The enzyme was maximally active towards sucrose than to raffinose and sucrase activity was significantly inhibited by bivalent metal ions and reducing group agents. The results indicated that due to changes in aggregation pattern, molecular organization of purified sucrase, produced in high sucrose medium, was altered and was different from the previously reported enzyme. This is the first report of a sucrase of such low size showing activity.     

Regulation of the Skeletal Muscle Ryanodine Receptor/Ca2+-release Channel RyR1 by S-Palmitoylation

The ryanodine receptor/Ca²⁺-release channels (RyRs) of skeletal and cardiac muscle are essential for Ca²⁺ release from the sarcoplasmic reticulum that mediates excitation-contraction coupling. It has been shown that RyR activity is regulated by dynamic post-translational modifications of Cys residues, in particular S-nitrosylation and S-oxidation. Here we show that the predominant form of RyR in skeletal muscle, RyR1, is subject to Cys-directed modification by S-palmitoylation. S-Palmitoylation targets 18 Cys within the N-terminal, cytoplasmic region of RyR1, which are clustered in multiple functional domains including those implicated in the activity-governing protein-protein interactions of RyR1 with the L-type Ca²⁺ channel Ca_V1.1, calmodulin, and the FK506-binding protein FKBP12, as well as in “hot spot” regions containing sites of mutations implicated in malignant hyperthermia and central core disease. Eight of these Cys have been identified previously as subject to physiological S-nitrosylation or S-oxidation. Diminishing S-palmitoylation directly suppresses RyR1 activity as well as stimulus-coupled Ca²⁺ release through RyR1. These findings demonstrate functional regulation of RyR1 by a previously unreported post-translational modification and indicate the potential for extensive Cys-based signaling cross-talk. In addition, we identify the sarco/endoplasmic reticular Ca²⁺-ATPase 1A and the α_1S subunit of the L-type Ca²⁺ channel Ca_V1.1 as S-palmitoylated proteins, indicating that S-palmitoylation may regulate all principal governors of Ca²⁺ flux in skeletal muscle that mediates excitation-contraction coupling.     

Reactive oxygen and nitrogen species during meiotic resumption from diplotene arrest in mammalian oocytes

Mammalian ovary is metabolically active organ and generates by‐products such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) on an extraordinary scale. Both follicular somatic cells as well as oocyte generate ROS and RNS synchronously and their effects are neutralized by intricate array of antioxidants. ROS such as hydrogen peroxide (H₂O₂) and RNS such as nitric oxide (NO) act as signaling molecules and modulate various aspects of oocyte physiology including meiotic cell cycle arrest and resumption. Generation of intraoocyte H₂O₂ can induce meiotic resumption from diplotene arrest probably by the activation of adenosine monophosphate (AMP)‐activated protein kinase A (PRKA)—or Ca²⁺‐mediated pathway. However, reduced intraoocyte NO level may inactivate guanylyl cyclase‐mediated pathway that results in the reduced production of cyclic 3′,5′‐guanosine monophosphate (cGMP). The reduced level of cGMP results in the activation of cyclic 3′,5′‐adenosine monophosphate (cAMP)‐phosphodiesterase 3A (PDE3A), which hydrolyses cAMP. The reduced intraoocyte cAMP results in the activation of maturation promoting factor (MPF) that finally induces meiotic resumption. Thus, a transient increase of intraoocyte H₂O₂ level and decrease of NO level may signal meiotic resumption from diplotene arrest in mammalian oocytes. J. Cell. Biochem. 111: 521–528, 2010. © 2010 Wiley‐Liss, Inc.     

Multiple chromosomal rearrangements in a hybrid zone between Littorina saxatilis ecotypes

Both classical and recent studies suggest that chromosomal inversion polymorphisms are important in adaptation and speciation. However, biases in discovery and reporting of inversions make it difficult to assess their prevalence and biological importance. Here, we use an approach based on linkage disequilibrium among markers genotyped for samples collected across a transect between contrasting habitats to detect chromosomal rearrangements de novo. We report 17 polymorphic rearrangements in a single locality for the coastal marine snail, Littorina saxatilis. Patterns of diversity in the field and of recombination in controlled crosses provide strong evidence that at least the majority of these rearrangements are inversions. Most show clinal changes in frequency between habitats, suggestive of divergent selection, but only one appears to be fixed for different arrangements in the two habitats. Consistent with widespread evidence for balancing selection on inversion polymorphisms, we argue that a combination of heterosis and divergent selection can explain the observed patterns and should be considered in other systems spanning environmental gradients.     

Seed‐induced Aβ deposition is modulated by microglia under environmental enrichment in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) is characterized by severe neuronal loss as well as the accumulation of amyloid‐β (Aβ), which ultimately leads to plaque formation. Although there is now a general agreement that the aggregation of Aβ can be initiated by prion‐like seeding, the impact and functional consequences of induced Aβ deposits (Aβ seeding) on neurons still remain open questions. Here, we find that Aβ seeding, representing early stages of plaque formation, leads to a dramatic decrease in proliferation and neurogenesis in two APP transgenic mouse models. We further demonstrate that neuronal cell death occurs primarily in the vicinity of induced Aβ deposits culminating in electrophysiological abnormalities. Notably, environmental enrichment and voluntary exercise not only revives adult neurogenesis and reverses memory deficits but, most importantly, prevents Aβ seeding by activated, phagocytic microglia cells. Our work expands the current knowledge regarding Aβ seeding and the consequences thereof and attributes microglia an important role in diminishing Aβ seeding by environmental enrichment.